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High-quality source rocks in saline lacustrine or marine sedimentary environments often show early peak petroleum generation and enhanced hydrocarbon yields, which have conventionally been attributed to organosulfur-enhanced thermal decomposition of kerogen. However, there is increasing awareness that the coexisting inorganic salts, particularly sulfates, might also contribute to the acceleration of petroleum generation. In this study, we investigated the influence of sulfates on the thermal decomposition of kerogen sampled from the Pingliang Formation in the Ordos Basin. Our results demonstrate that the kerogen samples mixed with sulfate generate more hydrocarbons with a lower peak production temperature than their sulfate-free counterparts. Detailed chemical analysis revealed that the presence of sulfates significantly facilitated the generation of resins and asphaltenes at temperatures below 350 °C, corresponding in our simulations to the early stage of petroleum generation (Easy%Ro

Combined with NMR, core experiment, slim-tube tests, nano-CT and oil composition analysis, the mechanism of CO2 enhanced oil recovery had been studied. CO2 flooding under supercritical state could achieve higher oil recovery. In the process of crude oil displaced by supercritical CO2, the average oil recovery was 46.98% at low displacement pressures and 73.35% at high displacement pressures. The permeability of cores after CO2 flooding was only 28%–64% of those before flooding. As to the expelled oil, the contents of asphaltenes and non-hydrocarbons decreased, and saturated hydrocarbons of above C25 were absent in some samples, indicating that they had been retained in cores as demonstrated by CT and NMR experiments. In slim-tube tests, the heavy components of oil were expelled when the pressure increased to 30 MPa. There was a reasonable bottom hole pressure (BHP) below which the heavy components driven out from the far-well zone would deposit in the near-well zone, and when the pressure was too high, the nonhydrocarbon detention may cause block. The smaller throat and worse physical properties the porous media had, the higher displacement pressure would be required to achieve a good oil displacement efficiency. The increase in displacement pressure or time of interaction between oil and CO2 could effectively enhance oil recovery.

This study aims to theoretically investigate the performance of an ionic liquid-based hydrophobic deep eutectic solvent (HDES), methyltrioctylammonium chloride:glycerol (1:2), as an asphaltene depo...

Asphaltene studies have been a prime focus topic for many decades. However, the underlying interaction mechanisms between water, oil, and asphaltenes requires more attention. Water is involved in a...

Nanotechnology is widely recognized for having important applications in many industries, one of which is oil and gas. Both environmental and cost benefits can be achieved when using nanoparticles for the separation of water and oil or further purification of produced water. More efficient emulsion separation can be achieved by selective adsorption of naturally present stabilizing components or magnetic action applied to nanoparticle-tagged droplets. The focus of this review is given to both nanoparticles and nanocomposites that have been studied with respect to asphaltene adsorption, crude oil demulsification, and produced water treatment, as well as oil spill cleanup and improvement of antifouling resistance of filtration membranes. Asphaltene chemistry and its role in emulsion stabilization are discussed in detail.

The purpose of this work was to investigate the effects of polystyrene-based acidic copolymers and ionomers on the dispersion of asphaltenes in heavy oil. In the first part of the work, we studied ...

There is a limited understanding of the microscale interactions between fluid–oil–solid interfaces, which could be a stumbling block to the development of relevant technologies and industries. With...

International audience

Subfractionation of asphaltenes based on their interfacial activity has begun to highlight critical differences between those asphaltenes that are strongly interfacially active (IAA) and the remaining asphaltenes (RA). Following the methods of petroleomics, representative structures of the two asphaltene fractions were determined, reflecting differences in abundant heteroatom groups, carbon number, double-bond equivalents, and single-core/multicore motifs. Using atomistic-potential-based grid-search methods, the intermolecular interactions between asphaltene–asphaltene and asphaltene–solvent (water, heptane, and toluene) were rapidly screened to identify the most favorable and therefore most likely intermolecular interactions to occur. Asphaltene–water interactions were stronger for IAA (abundance-weighted average interaction energy of −9.29 kJ/mol) than for RA (−6.32 kJ/mol), with hydrogen bonding more significant in the IAA–H2O interaction. Dimer interactions of IAA–IAA were stronger than RA–RA, and from the top 100 most favored interactions, the contribution to the total interaction energy was almost exclusively van der Waals for RA–RA (only 3% electrostatic), while for IAA–IAA, electrostatic interactions (9%) and hydrogen bonding (2%) were significant contributors in the most favored interactions. As the relative contribution of the electrostatic interaction increased, the dimer orientation less resembled that of a π–π stack. With the conception of petroleomics and large structural databases, the grid-search method is a useful atomic/molecular screening approach that provides an ideal triaging tool to rapidly assess a wide range of different molecular structures and interactions. The method is complementary to the more computationally expensive precision molecular modeling tools that are not suited to such workflows.

Cracking of high-sulfur natural bitumen of the Mordovo-Karmal and Ashalchi fields (Russia, Republic of Tatarstan) at a temperature of 450°C and different process times was studied. The characteristic features of the changes in the material and group compositions of the cracking products and the nature of the transformation of the group composition of the sulfur-containing compounds of oils as dependent on the cracking conditions were demonstrated. The kinetic regularities of the formation and decomposition of benzo- and dibenzothiophene derivatives in the cracking products of the natural bitumens were elucidated. Cracking was shown to involve breakdown of large molecules (resins and asphaltenes) with formation of a broad range of low-molecular-weight sulfur-containing compounds falling into oils. The sets of benzo- and dibenzothiophene homologs thereby formed were identical, but the rates of formation and decomposition of the sulfur-containing compounds were dependent on the thermal stability of the components of the initial bitumens. The data obtained provide a substantially better understanding of the laws governing the transformation of the sulfur-containing compounds of heavy hydrocarbon feedstock in thermal processes.

International audience; Recent advances in instrumentation for high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have enabled access to ∼70 »000 unique molecular formulas in broadband mass spectral characterization of unfractionated/whole asphaltenes. The results accumulated over a decade highlight the need for an asphaltene molecular model that acknowledges the coexistence of (1) monofunctional and polyfunctional species; (2) island and archipelago structural motifs; and (3) heteroatom-depleted/highly aromatic compounds, as well as atypical species with low aromaticity but increased heteroatom content. Collectively, results from FT-ICR MS, preparatory-scale separations (extrography/interfacial material), gel permeation chromatography, precipitation behavior in heptane:toluene, thermal decomposition, and aggregate microstructure by atomic force microscopy (among other techniques), suggest that the strong aggregation of asphaltenes results from the synergy between several intermolecular forces: π-stacking, hydrogen bonding, London forces, and acid/base interactions. This review presents general features of asphaltene molecular composition reported over the past five decades. We focus on mass spectrometry characterization and expose the reasons why early results supported the dominance of single-core motifs. Then, the discussion shifts to recent advances in instrumentation for high-field FT-ICR MS, which have enabled the detection of thousands of species in asphaltene samples, whose molecular composition and fragmentation behavior in ultrahigh vacuum agree with the coexistence of single-core and multicore structural motifs. Furthermore, evidence that highlights the limitations of commercially available/custom-built ion sources and selective ionization effects is presented. Consequently, the limitations require separations (e.g., chromatography, extrography) to gain more-comprehensive molecular-level insights into the composition of these complex organic mixtures. The final sections present evidence for the role of aggregation in selective ionization and suggest that advanced characterization by both thermal desorption/decomposition and liquid chromatography with online FT-ICR MS detection can be employed to mitigate the effects of aggregation and provide unique insights in molecular composition/structure.

The relevance of the study is related to the prospects for deep processing of solid fuel and the need to obtain more detailed information about the basic laws of thermal transformations of coal during its liquefaction. The development and improvement of direct coal liquefaction technologies in the future can become an important source of additional hydrocarbon resources for the chemical industry and power engineering. The main aim of the research is to study the effects of technological parameters (temperature and pressure) on liquefaction and thermal transformations of Barzas coals in carbon dioxide and hydrogen atmospheres in order to establish the relationships between thermal treatment conditions of coal feedstocks and the compositions and yields of its conversion products. Objects: sapromixites of the Barzas coal deposit (Kemerovo region, Russia) and products of their thermal transformations in carbon dioxide and hydrogen media. Methods: heat treatment of the coals studied in a laboratory microautoclave in various media (CO2, H2) and analysis of the products of their transformations by elemental analysis (CHNOS), FTIR spectroscopy and mass spectrometry. The studies were carried out on calibrated and serviceable equipment. The list of equipment and methods used in the given work are described in detail in the experimental part of this article. Results. Almost similar temperature and pressure dependences (extremal type curves) have been revealed for both the changes in the IR absorption intensities of alkyl groups and the yields of «coal liquids» (total amounts of maltenes and asphaltenes) in the process of Barzas coals transformations in carbon dioxide and hydrogen media. Differences in the transformations of two modifications of Barzas sapromixites were established, and a predominantly paraffin-naphthenic character of the functional composition of the resulting «coal liquids» was revealed. A clear relationship was found between the yields of gaseous products and atomic ratios H/C in the solid products of transformations of the Barzas sapromixites. «Coal liquids» and gaseous compounds obtained as a result of Barzas coals thermal processing can serve as potential raw materials for production of hydrocarbons and other valuable chemical products, as well as used as a fuel in production of heat and electricity.

The relationships of the reaction of the of tar asphaltenes with concentrated nitric acid were studied under various quantitative, temperature, and time conditions. According to IR spectroscopic data, nitration occurs to the highest degree during the action of a 50-fold excess of 64% nitric acid on the asphaltenes at 60°C for 4 hours. Nitration is accompanied by oxidation side reactions leading to the formation of nitrate, phenolic, carbonyl, and sulfoxide groups. It was established by mass spectrometry that there is a tendency for the number-average and weight-average molecular weights of the nitration products to decrease in comparison with the initial asphaltenes. It was found by electron paramagnetic resonance that the content of stable free radicals and vanadyl complexes in the products of the nitration reaction decreases.

Abstract Asphaltene-containing deposits formed on the CaF2 window induced by n-heptane flow in a microfluidic device have been investigated using an IR microscope and an imaging macro chamber (IMAC) with FPA detection. This is the first example of the ex situ infrared imaging of the deposits from crude oil formed under dynamic conditions of flocculant flow. It has been shown that fast aggregation of asphaltenes in n-heptane flow leads to the formation of deposit rich in heteroatom-containing functional groups: (О–Н, N–H, C=O, C–O, and S=O).

The transformations undergone by the high-molecular-weight heteroatomic compounds (resins, asphaltenes) of the Novokuibyshevsk Refinery vacuum residue during thermal cracking at 500°C in the presence of additives such as calcium carbonate and calcium acetate were studied. The characteristic changes in the composition of the cracking products depending on the amount of the additive were demonstrated. Based on the data from 1H NMR spectroscopy, elemental analysis, and molecular weight measurements, the structural-group parameters of the resin and asphaltene molecules in the original vacuum residue and in the products of its cracking in the presence of different amounts of the additives were determined. The heterogeneous additives (≤0.5 wt %) afforded deeper degradation of resins and asphaltenes. The resin molecules underwent compaction due to destruction of the saturated rings and aliphatic moieties, followed by an increase in the content of oils in the liquid cracking products composition.

Algerian crude oil displays a marked propensity for asphaltene precipitation, leading to solid deposits during extraction, transportation, and storage. The relationship between precipitation and chemical composition is unclear; in fact, Algerian crude oil actually features a low asphaltene concentration, despite its relatively large rate of deposit formation. The rationalization of the precipitation process and its remediation should benefit from a molecular characterization of the crude oil. In this study, two unstable asphaltene fractions (A1 and A2) from two different deposits, and two resin crude oil fractions (R1 and R2) from the Hassi-Messaoud Algerian field have been characterized at the molecular level by means of high-resolution mass spectrometry with an Atmospheric Pressure Chemical Ionization (APCI) source. Positively and negatively charged compounds with molecular weights 200−1200 m/z were detected. Several thousand molecular stoichiometries were identified and classified for each sample, in terms of heteroatom content and aromaticity, searching for trends characteristic of the two asphaltenes and of the associated resins. The A2 asphaltene, from a downstream storage tank, displays a higher aromaticity and O heteroatom content, which correlates with an enhanced aggregation propensity, in comparison to the A1 fraction, collected at the well bore. The resin fractions are found to be abundant in aliphatic hydrocarbons and heteroatomic compounds of moderate aromaticity. The more polar resin fraction, R2, is enriched in N-containing species, with respect to the less polar resin fraction R1, which correlates with the stabilizing function observed in previous works. The results stress the view of crude oil fractions as complex mixtures, rather than in terms of average prototypical compounds, when facing the understanding of asphaltene deposition conditions., Area of Physical Chemistry

Chemical inhibition of asphaltene deposition is considered a cost-effective way to prevent the harsh consequences of asphaltene instability in the produced crude. Thus, a careful screening of asphaltene inhibitors is crucial for an efficient prevention. However, the characteristics of asphaltenes such as their acid–base properties will influence the selection of an asphaltene inhibitor and the inhibition mechanism. Therefore, improved knowledge on asphaltene acidic and basic fractions is important. In this work, the separation of asphaltenes into acid, base, neutral, and amphoteric fractions was performed. Among the existing techniques to fractionate asphaltenes, the method of Ramljack was adopted and applied on a light oil extracted asphaltene. However, this oil was sampled from one of the wells in the Hassi Messaoud field in Algeria that experienced a recurring deposition of asphaltenes. The results of asphaltene fractionation reveal that the half composition of this heavy part of crude oil is active functions gathered acid and base components. However, the main contribution is reported to the neutral fraction. The characterization results of infrared and elementary analyses show that both active fractions are aromatic and polar. Moreover, the acid fraction contains in its structure carboxylic acids, phenols, sulfoxide groups, and aliphatic chains, while the structure of the base fraction contains amines, sulfoxide groups, and aliphatic chains.

The covalently bound biomarkers in the macrostructure of kerogen or asphaltene can provide unique information compared with the routinely extractable biomarkers. Here, a shale sample (immature Posidonia Shale) and an oil sample (Norwegian Geochemical Standard NSO-1) were systematically investigated by heating them to different temperatures and by mixing them with different catalytic materials to optimize the microscale sealed vessel catalytic hydrogenation (MSSV-Hy) protocol. It can be demonstrated that (1) tetralin acts as an effective hydrogen donor to stabilize the generated free radicals in the pyrolysis system enabling the bound biomarkers to resemble more closely their free counterparts, (2) PtO2 is the most appropriate catalyst for promoting the overall release of bound biomarkers, and (3) 390 °C is the best end temperature (from 200 °C at 0.7 °C/min) for the MSSV-Hy approach, balancing between bound biomarker yields and the protection of the original biomarker steric configurations. MSSV-Hy is a quick, highly reproducible, less sample demanding, and cost-effective method to release bound biomarkers and has great potential for studying the carbon cycle in its broadest sense.

Considering numerous issues due to asphaltene precipitation during production and transportation of crude oil, this work aims to postpone the onset point of asphaltene and improve the stability of its colloids in heavy (S) and light oil (D) samples. For this purpose, water/oil interfacial tension (IFT) is measured to evaluate the effect of surfactants as asphaltene inhibitor on heavy and light oil samples from Iranian south fields. Onset of precipitation from oil samples is revealed by sudden change in IFT between deionized water and oil samples through addition of different fractions of n-heptane as precipitant. Surfactants are used to stabilize the asphaltene colloids and prevent asphaltene precipitation from crude oil. However, crude oils of different properties require investigations for appropriate surfactant at optimum concentration to delay asphaltene precipitation. In this work, three surfactants Linear dodecyl-benzene-sulfonic acid (L–DBSA), dodecyl resorcinol (DR) and nonylphenol (NP) are examined for their retarding capabilities of onset point of asphaltene precipitation in oil samples S and D. Also, the involved mechanisms for addition of surfactant to crude oil are analyzed and interpreted. Enhanced stability of crude oil and degree of postpone in onset point follows the order of L–DBSA > DR > NP for heavy oil S and NP > DR > L–DBSA for light oil D owing to nature and chemical structure of surfactants and also properties of crude oil samples. Furthermore, IFT fluctuations for light and heavy oil are similar but the faster onset point and different values of IFT for light oil arise from unstable nature and density difference.

An algorithm is proposed for determining the rate of organic deposits formation, which consists in calculation of the distribution of temperatures of the inner surface of a hollow-rod string and in laboratory studies on a “cold rod” unit, taking account of calculated temperatures. The proposed algorithm was tested in a target transit production oil well of the Pavlovskii oil field in the Perm Krai (Region) of the Russian Federation. The proposed algorithm allowed determination of the variation of the organic deposits formation rate along the length of the hollow-rod string and of the depth at which the deposit formation rate is maximal. Laboratory studies were conducted to determine the effectiveness of deposit removal from the hollow-rod string by chemical method involving use of inhibitors of asphaltene-resin-wax deposit formation as well as by solvents.

The yields of coal liquids (maltenes and asphaltenes) formed upon the heat treatment of three low-metamorphosed Kuzbass coals with different hydrogenation ability parameters in an atmosphere of hydrogen were compared. It was found that the H/C atomic ratios, the yields of volatile substances, the relative maximum rates of pyrolysis of coals in a range of 300–500°C, and the ratios between aliphatic and aromatic structures [(D2920 + D2860)/D1600] in the test coals increased linearly with an increase in the yields of liquid products in the order Karakan long-flame coal 1.5 and the yield of gases (~10.3 wt %) was lower by a factor of >2 than those in similar experiments with the gunny-like coal.

Quantitative liquid 1H and solid 13C CPMAS NMR spectroscopy were used in combination with qualitative DEPT (Distortionless Enhancement by Polarization Transfer) and liquid 13C NMR to investigate the molecular structural parameters of an Algerian asphaltenes. The molecular weight of the asphaltene ionisable species determined by positive Electro Spray Ionization mass spectrometry ESI was around 390 Da. The results indicate that the representative molecular structure of the asphaltenes contains PAH (Poly-aromatic hydrocarbon) core of 4–5 rings. The combination of 13C NMR/DEPT constitutes a good route for characterizing the chemical functions of asphaltenes.

Carbonate acidization is the process of creating wormholes by injecting acid to increase reservoir permeability and oil production. Nevertheless, some reservoir oils are problematic with low asphaltene stability, which affects the wormholing process. The interactions between acid, rock, and asphaltene lead to acid-asphaltene sludge formation, which reduces oil productivity and acid injectivity. Neglecting this sludge formation leads to over predicting the depth of the wormhole penetration. Therefore, a numerical model was developed in this study to provide a better understanding of acid-asphaltene sludge formation effect on wormhole creation and propagation in carbonates. A one-dimensional radial model was developed by coupling fluid flow equations in porous media with asphaltene deposition and acid-asphaltene reactions. Then, the developed model was validated and utilized to investigate the effects of different parameters on wormholing including asphaltene presence, acid injection volume and concentration, formation temperature and porosity, and asphaltene concentration. Results showed that acid injection in carbonates with asphaltenic oils reduce wormhole penetration from 40% to total pore blockage as opposed to reservoirs without asphaltene deposition. The findings also highlighted that shallow wormhole penetration is more pronounced with a high volume of acid injection, high porous formations, less diluted acid, and a high concentration of asphaltene. In addition, there is an optimum acid injection volume at which wormhole penetration is high and its infiltration is deep into the formation. This is the first work to discuss modeling of acid-asphaltene sludge formation and subsequent wormhole development in carbonates, which is particularly important for problematic crude oils.

Heavy oils are sometimes diluted with petroleum solvents for pipeline transportation, and it is necessary to ensure that the selected solvent does not precipitate asphaltenes from the oil. The modified regular solution (MRS) model can predict asphaltene precipitation from heavy oil diluted with pure n-alkanes but has not yet been applied to petroleum solvents. To do so, asphaltene precipitation data were measured for bitumen diluted with petroleum solvents including gas condensates, diesels, kerosene, and naphtha and their blends with n-heptane. The petroleum solvents were characterized into single carbon number (SCN) fractions on the basis of gas chromatography assays. New correlations were proposed for the molecular weight, density, and solubility parameters of the SCN fractions. The MRS model with the characterization and correlations matched asphaltene precipitation data with an average absolute deviation of 0.7 wt % for petroleum solvents with relatively low contents of pure aromatic and cyclic components ( 10 wt %). Hence, the proposed model is currently limited to solvents similar to condensates, diesels, and kerosenes.

Non-aqueous foams are much less studied than aqueous foam systems, although non-aqueous foams are important in many industries like petroleum refining. In this study, the foamability of non-aqueous...

Poly(styrene-co-maleic anhydride)s (SMAs) with different compositions and molecular weight were synthesized through the reversible addition–fragmentation chain transfer polymerization technique. SMAs were converted to poly(styrene-co-octadecyl maleimide)s (SNODMIs) by amidation with octadecyl amine and subsequent imidization. SNODMIs with octadecyl branches were evaluated as flow improvers in the model crude oil with a high content of asphaltenes. The effects of molecular structures, including molecular weight, branch content, and imidization degree, on the effectiveness of SNODMI in reducing the viscosity and yield stress and improving the morphologies of asphaltene particles were thoroughly investigated using a rotational rheometer with parallel plate geometry and a polarizing microscope with a hot stage, respectively. It has been found that efficacy of SNODMI in reducing the viscosity and yield stress of the model crude oil increases with an increasing branch content of SNODMI. (alt)SNODMI with the highest branch content, approximately 45 mol %, achieved the best performance. Too high or too low molecular weight is not beneficial for SNODMI to improve the flow ability of the model crude oil. The appropriate molecular weight (Mₙ = 3500 Da) is required to achieve the optimal effectiveness. The optimal imidization degree of SNODMI is 100% and is independent of the branch content. The addition of SNODMI in a real crude oil has reduced the viscosity and yield stress by more than 90%.

The paper describes a process of crude oil differentiation in an oil reservoir induced by an inflow of light hydrocarbons. It was shown that when an oil-rich carbonate rock is destabilized the redistribution of oil components occurs due to the adsorption and/or precipitation of asphaltenes on the rock and their gravitational separation. More compact asphaltene aggregates concentrate in the bottom of the oil reservoirs model.